Method and apparatus for hydrolyzing cellulosic materials



March 20, 1956 L. C. WALLACE ETAL METHOD AND APPARATUS FOR HYDROLYZING CELLULOSIC MATERIALS Filed June 14. 1952 2 Sheets-Sheet I pun/vs 1.. KEN/76H March 20, 1956 c. WALLACE ETAL 2,739,036

METHOD AND APPARATUS FOR HYDROLYZING CELLULOSIC MATERIALS Filed June 14, 1952 2 Sheets-Sheet 2 INVENTORS LEW/5 c. WflLL/ICE Rem/l5 c. SPROULL ova/v5 L. KE/WMA United States Patent METHOD AND APPARATUS FOR HYDROLYZ ING CELLULOSIC MATERIALS Lewis C. Wallace, McAllen, Tex., Reavis C. Sproull, Savannah, Ga., and'Duane L. Kenaga, Midland, Mich, assignors of twenty-live per cent to Tennessee Coal & Iron Division, United States Steel Corporation, a corporation of New Jersey, and seventy-five per cent to Nickey Brothers, Inc., a corporation of Tennessee Application June 14, 1952, Serial No. 293,556

17 Claims. (Cl. 127-4) This invention relates to a method and apparatus for treating cellulosic materials, and has for its principal object the provision of a two-stage continuous process for producing both furfural and hexoses from cellulosic materials in general, such as wood waste, saw dust and the like.

Another object of our invention is to provide a process for treating cellulosic materials in two stages, in which the cellulosic material is first treated with a material in the vapor state and secondly with a material in liquid state thus first removing the volatile products formed and then removing soluble materials.

Another object of our invention is to provide a method and apparatus of the character designated which shall produce concomitantly maximum percentages of both furfural and hexoses thus reducing the cost of producing the same and making it feasible to hydrolyze a large variety of cellulosic materials.

A further object of our invention is to provide a method and apparatus for producing continuously both furfural and hexoses from cellulosic materials which shall yield a wood sugar liquor substantially free of pentoses, thus enhancing its value as stock feed or for use as a fermen tation substrate.

A further object of our invention, is to provide a method and apparatus for obtaining furfural and hexoses from cellulosic materials which shall produce a relatively unpolymerized lignin residue, which is suitable for many uses, such for example as a reactive filler in phenolic resins, plastics and similar compounds.

A more specific object of our invention is to provide a method and apparatus of the character designated in which a pre-acidified cellulosic material is passed continuously through a first stage pressurized zone in contact with countercurrently flowing steam or with countercurrently flowing steam and acidic or neutral gases and the residual cellulosic material is passed through a secondstage pressurized zone in contact with a countercurrently flowing hydrolyzing solution.

Heretofore in the art to which our invention relates furfural has been obtained from cellulosic materials by acidifying ground cellulosic material and subjecting it to batchwise steaming in a digester for relatively long periods of time. The steam and vapors are vented con-. tinuously from the apparatus to remove the furfural obtained from the pentosans. The residue comprises primarily lignin, hydrolysis-resistant cellulose, and humic substances resulting from the decomposition of hydrolysisreleased sugars.

Eiforts have been made to develop a two-stage continuous process which would produce high percentages of furfural and permit the economic recovery of 6-carbon sugars from the residual cellulose by re-hydrolysis. While these processes give satisfactory yields of pentoses and good separation of pentoses and hexoses, they require expensive secondary processes to convert the pentoses to furfural. Furthermore, the residue resulting from these processes has been found to be extremely resistant to re- 2,739,086 Patented Mar. 20, 1956 ice hydrolysis. Selected agricultural residues contain sulficient furfural precursors to permit economic processing for furfural alone. However, this is not true of wood and cellulosic materials in general.

To overcome the above difficulties, we have devised a two-stage continuous process for producing both furfural and hexoses from cellulosic materials. We are enabled to accomplish this by first removing the furfural in an atmosphere of vapor and then removing the sugar in an aqueous medium, both reactions being catalyzed by mineral acids.

Apparatus embodying features of our invention and which may be used to carry out our improved method is illustrated in the accompanying drawings forming a part of this application, in which:

Fig. 1 is a diagrammatic elevational view of the apparatus;

Fig. 2 is a sectional elevational view;

Fig. 3 is an enlarged detail view showing a means for introducing steam adjacent the lower end of the upper reaction zone and a means for removing sugar liquor adjacent the upper end of the lower zone;

' Fig. 4 is a detail sectional view showing the bottom of the lower section of the reaction chamber and the lignin discharge valve; and,

Fig. 5 is a plan view of the apparatus with the reactionchamber removed and taken along the line V-V of Fig. 4.

Referring now to the drawings for a better understanding of our invention, we show a feed hopper 10 for receiving the cellulosic material to be hydrolyzed. Communicating with the feed hopper 10 is a horizontally extending housing 11 having an open top. The cellulosic material is withdrawn from the hopper 10 by means of a feed screw 12 which is mounted for rotation in the housing-11. The cellulosic material may be acidified as by soaking in dilute acid before being supplied to the feed hopper 10 or it may be sprayed with acid after entering the apparatus by means of a spray nozzle 13 positioned above the opening housing 11.

The discharge end of the feed screw housing 11 communicates with a vertically extending housing 14 tapering inwardly from top to bottom. Mounted for rotation in the housing 14 is a feed screw 16, which is also tapered inwardly from top to bottom thereof. As will appear the cellulosic material is compressed by the vertical-feed screw 16 so as to form a steamtight plug adjacent the tion 21 of a reaction chamber indicated as a Whole by' numeral 22. The upper section 21 has downwardly flaring side walls to facilitate downward flow of solids against upwardly flowing fluids. On top of the section 21 is a frusto-conical section 23 which is preferably made separable from the section 21, as at 24, to facilitate assembly and dismantling of the apparatus. Annular flanges 26 and 27 are provided for securing sections 21 and 23 together.

Secured to the lower endof the vertically extending housing 14 and spaced inwardly of the side walls of. section 23 is a filter screen 28 having a lower annular flange 29 which fits between the flanges 26 and 27 thus securing the filter screen in place. The flanges 26, 27 and 29 are secured together by any suitable means such as bybolts 30. Vapors escape from the upper section 21 of the reaction chamber into the annular'chamber 31 defined between the side walls of the filter screen 28 and the .frusto-conical section 23. Communicating with the chamber 31 through a wall of thesection 23 is' a vapor oflE-take conduit 32 having a regulating valve 33 therein. The vapors pass froni'jthe conduit 32 toIconventional furfural recovery apparatus indicated generally at 34. l i

The descending cellulosic material acts as a filter bed to prevent lig nin fines from reaching the filter scre en 28 thus making it possibleto provide openings 36 inthe filter screen of such size as to be substantially nonfclog'ging. Preferably the openings 36 are around inch in 'ine'te'r and are drilled at an angle ofapprog imately 45Qwi'th respect to the walls of the frustoconicalfilter 28 and slope inwardly in the direction of i the flow of k cellulose mater'ial. Thedo WnwardIy moving cellulqsiicrnaterial tends to scrape out any splinters or the like which might be lodged in the filter screen.

Section 21 of the reaction chamber is provided .withan outwardly extending annular flange 137 at the bottom thereof. Positioned beneath the section not the reaction chamber is a lower section indicated as a whole by the numeral 38 and having an outwardly extending annular flange 39 at the top thereof. Positioned between the flange 37 of section 21 and flange 39 of the lower section are upper and lower annular blocksgtl and 4 2, respectively. The inner circumference of .the annular block 41 is provided with an annular groove' 43 and theinner circumference of the block 42 is provided with an annular groove 44. The annular block 41 is separated from the annular-block 42 by asuitable gasket 46' which forms a fluidtight joint therebetween. Similar gaskets 47 and .48 are placed between the annular flange 37 and the block 41 and between the annular flangej39 and theblockAZ. Positioned within the annular block 41 .is a cylindrical screen plate 49 having an outer circumference equalsubstantially to the inner circumference of the annular block 41. Positioned within the annular block 42 is' a cylindrical screen plate-51 having an outer circumference equal substantially to the inner circumference of the annular block 42. Theflange '37 is secured to theflange 39 by a plurality of bolts 52, thus securing the section 21 to the section'38 and clamping the annular. blocks 41 and 42 with their associated screen plates in place. i

The upper screen plate 49 is proyided with a plurality of openings 53 and the lower screen plate Sliis provided with a plurality of openings 54. C ornnij;rg ti fi lg ly'ith, the annular opening 43 in the upper block 41 a re*'a plurality of horizontally extending openings 56. 1 Communicatingwith each of the openings 56: is asteam pipe' 57 having a regulatingvalve 57a therein. The steam'enteri ng the annular groove 43 from" the steam .pipes 57 passes through theopenings 53 to the interior. of itheJe ac on chamberthence upwardly through downwardly mov-' ing cellnlosic material. The openingssi and arelpreferably flared outwardly in the direction [of fluid lt'rayeh as shown in Fig. 3, thus providing self-cleaning,openings.

The lower block 42 is providcdwith a plurality of horizontally extending openings SSWhich communicatewith the annular groove 44 withwhich the, openings54 connect. Communicatingwith each of the, openings. 58, is a liquor discharge conduit 59 having' a regqlafin g valvelfiga therein. for removing the sugar v 1iquor,fromi' the' reaction;

chamber and conveying it to a flash chamber '60.

The-Walls of thelower section 3810f the reaction charnher are tapered inwardly toward the bottom. theredfito form a collecting section 38a. At the lower 'end or the section 38a is an inverted frusto-conical'bottpm or discharge section62 for the ligninsepa rated inithe re chamber. Attachedto the bottom 'of the lowetfi 38a and enclosing .the discharge sectionffilisaidis housing 63. Mounted in the lower endof tthe ,dis h ge housing 63 is a sleeve 64. --Eitting inanint ernallyihteaded portion 66 of the sleeve 64 opposite the discharge section 62 in an externally threaded"glan'd"671"Slidably fitting into the gland 67 is'a poppet valve 68 having a head 69 of a size and shape to slide in the sleeve 64 and seat against the lower end of the discharge section 62. The poppet valve is held in seated position by means of a back pressure spring 71 which surrounds the poppet valve between the head 69 thereof and the gland 67. The poppet valve 68 is opened briefly at timed intervals by suitable mechanical means, such as disclosed in the application for Letters Patent of Lewis C. Wallace, Serial No. 211,274, Method and Apparatus for Hydrolyzing Cellulosic Materials, filed February 16, 1951, which issued on June 22, 1954, as Pat. No. 2,681,876. The lignin passes from the discharge housing 63 through a conduit 72 to a suitable separator or lignin flash tank 73.

Communicating with th'e'lower section 38 of the reaction chamber adjacent the bottom thereof is a conduit 74. The hydrolyzing solution, such as water and a suitable acid is supplied tothe conduit 74 through pumps 76 and 7 7, respectively. The dilute acid is then introduced into the reaction chamber through an in1et'78 adjacent thebottomof the section 38a.

As shown in Figs. 4 and 5 the inlet 78 for the hydrolyzing solution communicates with a horizontally extending annular passage 79 formed in an annular block 81. The annular block 81 is positioned between a flange 82 at the lower end of the section 38a and a flange 83 extending outwardly from the discharge section 62 and is held in position by any suitable means such as bolts 84. The annular passage79. communicates with the interior of the lower .section 38a through a plurality of spaced apart,,upwardly extending openings 86. In the block 81 is a second annular passage,87,larger in diameter than passage 7:9,and disposed above passage 79, which communicates with the lower section.38a of the reaction chamber through a plurality of. inwardly and upwardly extending openings 88 positioned betweenthe upwardly extending openings 86. Steam isintroduced to the annular passage 87 through an inletconduit-89.

-From theforegoing description of apparatus, our improved method for producing both furfural and hexoses will be readily understood. For convenience of description, the portion of the reaction chamber above the liquor discharge ,conduit 59, or section 21, will be referred to as the,firststage zone, and that portion below the liquor dischargeconduit 59, orsection .38, will be referred to as the second-stage zone.

A suitably prepared cellulosicmaterlal, such as hardwood chips containing both furfural precursors and poly' anhydrohexoses is supplied to the, feed hopper 10. The cellulosic. material may be acidified before being supplied to th feedhopper 10, as by soaking in a dilute mineral acid such as sulphuric acid, or the cellulosic .materialmay be sprayed with acid from the nozzle 13. The acidified cellulosic, rnaterial, is couveyed, by the feed screw. 12 to the vertically extending housing 14 where.the vertical feed .screw 16 forces it downwardly to form a steamtight plug in the housing 14. Upon reaching the filter screen 28. the acidified material expands thus opening up the structure to the action of counterfiowing steam. Gravity together with the downward forceexerted by the feed screws 16 through the, continuouslyentering plug of cellulosic material, keep the solid materials moving steadi- 1y downward through the'first-stage reaction zone. Under the combined action of steam and theacid catalyst, peritosans in the cellulosic material are converted into furfural as represented by the following equations:

a Steam is introduced continuously under pressure through the annular groove 43 and passes upwardly through the descending bed of acidified material in the first-stage zone. Furfural vaporizes at the elevated temperatures employed and is swept along with the steam. The furfural bearing steam is separated from solid material by the filter screen 28 and is conveyed continuously to the furfural recovery unit 34 through conduit 32 at a rate controlled by the valve 33.

The residual cellulosic material from the first-stage zone is forced continuously downward into the secondstage zone, or section 38, of the reaction chamber. In the second-stage zone the residual cellulosic material is contacted continuously by counterflowing hot dilute acid. As hydrolysis progresses, the residual cellulosic material becomes sufiiciently softened and reduced in volume that it flows into the lower collection section 38a thence to the discharge section 62. The lignin is removed at regularintervals from the discharge section 62 by intermittently opening the poppet valve 68 by any suitable means, not shown.

The heated dilute acid for the hydrolysis zone or second-stage zone is prepared by mixing water with a concentrated mineral acid, such as sulphuric acid and steam. We have found in actual practice that a sulphuric acid solution having a concentration of approximately 1% (basis total liquor) is satisfactory in every respect. The mixing may be done externally, but preferably only the water and acid are mixed externally and the solution is introduced through the conduit 74 and inlet 78. The steam is then introduced separately through conduit 89. By introducing the steam and dilute acid at different points and preventing the same from mixing before entering the reaction chamber, the conduits, are protected against corrosion which would result from coming in contact with hot dilute acid.

The hot dilute acid in the second-stage zone converts the cellulose to sugar by hydrolysis. The reaction may he represented by the following equation:

(3) Acid (U0111005) 'IlHnO 3-? nCo nOo ea Polyanhydrohcxose hexose (cellulose) (Glucose) v The sugar dissolves rapidly in the ascending liquor and the liquor is separated from the solid material at the upper end of the second-stage zone by the cylindrical screen plate 51 and flows through conduits 59 to the flash chamber 60. The ascending liquor leaches residual sugars from the descending lignin. Gravity mixing of the acid liquor is prevented by the continuous unidirectional flow through the small interstices between the particlesof cellulosic material. The point at which complete hydrolysis is obtained should be as near the bottom of the'section 38a as possible so as to keep the reactor full at all times.

The following example shows typical results obtained with run-of-the-mill hardwood waste. The waste was chipped and screened to A to A2 inch mesh and soaked in cold 4% sulphuric acid. The chips were drained and fed into the reaction chamber at a uniform rate of approximately 83 lb./hr., dry wood basis. 50 gallons of water and 8 pounds of 66 B. sulphuric acid were mixed externally and injected through the acid inlet at the bottom of the reaction chamber. Also, sufiicient steam was introduced along with the acid to maintain a pressure of approximately 196 p. s. i. gauge. Approximately 100 lb./hr. supplementary steam was added through the steam inlet and the liquid level was maintained adjacent and below the steam inlet. Discharge rates were adjusted to give a wood dwelling time, in both reaction zones of about one hour, a liquor dwelling time of about 8 minutes and a furfural condensate of about 100 lb./hr. From each 100 pounds of wood, 6.96 pounds of furfural and 18V pounds of glucose were recovered.

-Commercial processes now employed recover approximately,7 '8% .of the theoretically available glucose and about of the theoretically available furfural. However, so far as we are aware, no process now employed approaches these yields for both products. This is due to the fact that successful processes now employed for recovering sugar give practically no furfural and maximum furfural yield is obtained only at the expense of degrading most of the potential glucose beyond recovery. From raw hardwood Waste containing 34% potential glucose and 13% potential furfural, present processes would obtain either 27% glucose or 9% furfural. When raw hardwood waste was hydrolyzed in accordance with our improved process not only is 77% of the maximum commercial yield of furfural obtained but also 66% of the usual commercial yield of glucose.

Steam for the first stage zone may be obtained wholly by flashing from the hot second stage liquid or by the introduction of the total first stage steam requirement through the conduit 57 adjacent the point where the sugar solution is removed from the second stage zone, or by a combination of the two. Acidic or neutral gases may be introduced into the first stage reaction zone along with or independent of, supplementary steam. The acidic gases catalyze the formation of furfural, while neutral gases reduce the partial vapor pressure of the furfural without appreciably increasing the partial vapor pressure of water. Also, the first stage reaction zone can be operated at steam pressures and temperatures appreciably .above those employed in the second stage zonedue to the relatively slow rate at which steam condenses on the surface of hot water.

By employing supplementary steam at a temperature slightly above that of the liquid two distinct advantages are obtained. First, it lessens the tendency of the liquid to be carried into the first-stage reaction zone by priming and foaming. Second, it permits the liquid level to be measured and controlled by thermocouples or similar devices, which are sensitive to temperature changes in the reaction chamber. The use of thermocouples eliminates the use of external float devices which are often put out of operation due to tar deposits, or the use of devices which are positioned within the reaction chamber, which interfere with the flow of solid materials therethrough.

From the foregoing it will be seen that we have devised an improved method and apparatus for producing both furfural and hexoses by the hydrolysis of cellulosic materials in general. By passing the cellulosic material through a first stage pressurized zone in contact with countercurrently flowing steam, and continuously removing the furfural bearing steam from the pressurized zone adjacent the place where the acidified cellulosic material is introduced, the removal of the furfural substantially as rapidly as it is formed is assured. Also, by passing the residual cellulosic material from the first-stage zone continuously into a pressurized second-stage zone where it comes in contact with a countercurrently flowing hydrolyzing solution at elevated temperatures, hexosans and the remaining pentosans are converted by hydrolysis into their corresponding sugars which dissolve in the counterflowing liquid.

While we have shown our invention in but one form,.

it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What we claim is: v

1. The method of producing furfural and hexoses from cellulosic materials which comprises the steps of, continuously bringing together under superatmospheric pressure preacidified cellulosic materials in countercurrent flow I with a hot gaseous medium whereby furfural is produced cpntinuously, removing the furfural continuously as it is produced adjacent the point the cellulosic materialsfare introduced, then passingcontinuously the residual cellulosic materials in countercurrent' flow witha hydrolyzin'g acid and steam whereby soluble hexoses are produced, removing the soluble hexoses Continuously adjacent the point said hot gaseous medium is introduced, and removing'the lignin substantially continuously adjacent the point said hydrolyzing acid and steam are introduced.

2. The method of treating cellulosic materials comprising the steps of continuously bringing together under superatmospheric pressure pr'eacidified cellulosic materials in countercurrent fiow jwith' steam whereby volatile products are produced, removing said volatile products continuously as they are produced adjacent the point the cellulosic materials are introduced, then passing continuously the residual cellulosic'materialsin countercurrent flow'with' a hot hydrolyzing acid "solution whereby sugar is produced, removing the sugar thus formed continuously adjacent the point steam is introduced and said rcsidual' cellulosic materials first contact said acid solution, and removingfthe lignin substantially continuously adjacent the point said acid solution is introduced. V

3. The method of'treating cellulosic materials comprising introducing continuously preacidified cellulosic materials at the upper end'of'a downwardly moving column thereof while maintaining said column under superatmospheric pressure, introducing continuously steam into'said downwardly moving column intermediate the ends thereof and in countercurrent flow to saidcellulosic materials, eX- panding the volume of said cellulosic materials while passing the same in countercurrcnt flow to said steam whereby volatile materials are produced, removing said volatile materials continuously as the same are released adjacent the point of cellulose expansion, introducing continuously at hot hydroly zing acid'adj'acent the lower end of said downwardly moving column in countercurrent flow to said cellulosic materials whereby a 'sugar'solution is produced, removing the sugar solution thus formed continuously ad-. jacent and below the point at'which said steam is introduced, and removing the lignin substantially continuously adjacent andbelow the pointsaid'hydrolyzing acid is .introduced.

fl. The method of treating cellulosic materials as defined in claim 3 in which the cellulosic materials flow in a substantially directly downwarddircction and the steam and hydrclyzing acid fiow upwardly through the cellulosic ma teria s. H

5. The method of treating cellulosic materials as defined in claim 3 in which thehydrolyzing acid employed is sulfuric acid. 4 i i 6. The method of treating cellulosic materials comprising the steps of introducing continuously cellulosicpreacidified materials at one endof anioving colum'nthe reof while maintaining said column under superatm'ospheric pressure, introducing steamjco'n'tinuously intosaid moving column intermediate the ends thereof and counter to the direction of movement of the cellulosic materials whereby volatile materials are produced, removing said volatile materials as they are produced adjacent the point the 'cellulosic materials are introduced, passing the residual column of cellulosic materials in countercurrent flowwith a hydrolyzing acid and steamwhereby the cellulose is converted into sugar, removing the sugar thus 'formed'adjacent the point steam first contacts said column intermediate the ends thereofandiremoving lignin adjacent the point said hydrolyaing acid and steam areintroduced. 7. The method of treatingcellulosic material s comprisi mg the steps of, introducing continuously preacidifiecl cellulosic materials at the upper end of a downwardly moving column thereof while maintaining said column tinder superatmospheri'c pressure, introducing steam'con ti nuously into said column intermediate the ends thereo f and counter to the direction of movement of said cellulosic materials whereby volatile materials'are produced, removing the volatile materials from said column adjacent the point the cellu H .rriateiialsare introduced, introducing con'nuo si fi upwardly'moving stream of hot hydrolyzing acid at' the lower'end of said column whereby a sugar solution is plfoduced, removing the sugar solution continuously frofmsa'id column adjacent and below the point the steam is'introdueed, and removing lignin substantially continuously' adjacent and below the point said hydrolyzing acid is introduced.

8. "The method of treating cellulosic materials as defined in -claim 7 in which at least a portion of said steam introduced is obtained by flashing from the hot hydrolyzing acid; i

' '9 The method of treating cellulosic materials comprising the steps 'of, introducing continuously preacidifid cellulosic materialsat the upper end of a downwardly moving column thereof while maintaining said column under superatmospheric pressure, introducing selectively steam, acidicgases and neutral gases into said column interniediate the ends thereof and counter to the direction of movement of said cellulosic materials whereby volatile materials'are produced, removing the volatile materials from s'aid'column adjacent the pointthe cellulosic mate'- rials are introduced, introducing continuously at hot bydrolyzingacid adjacent the lower end of said column counter to the direction of movement of the cellulosic materials whereby asugar solution is produced, removing said sugar solution continuously adjacent and below the point said steam, acidic gases and neutral gases are introduced, and removing lignin substantially continuously adjacent and below the point said hydrolyzing acid is introduced."

lQf'Apparatus for treating cellulosic materials comprisinga vertically extending reaction chamber having downwardly fiaring side walls at the upper portion thereof, the upper'portion ofsaid side walls forming an upright frustoconical top and the lower portion of said side walls formin'g'an invel'ted frusto-conical bottom, a frusto-conical filter screen secured to the inner surface of the sidewalls and spaced from said upper portion defining thercbetween a second chamber, a vapor off-take conduit communicating with said second chamber, feed means to introduce cellulosic material continuously under pressure adjacent the top of the reaction chamber, there being passageways in said side walls intermediate said filter screen and said frusto conic'al'bottom for introducing steam into said re action chamber, inlet passageways adjacent the bottom of said'reaction chamber for introducing a hydrolyzing acid, there being openings in said side Walls subjacent thefirst mentionedpassage'ways for removing sugar liquor, and ligitin"discharge"'rneans adjacent the bottom of'thereaction chamber.

11; Apparatus for treating cellulosic materials compris ing a verticallyextending reaction chamber embodying an upper and a lowersection, said upper section having downwardly flaring side Walls, feed means for introducing a cellulosic material continuously under pressure adjacent the top or the reaction chamber, 'a pair of superposed horizontally extending cylindrical screen plates between said upper section and said lower section, annnular blocks surrounding said screen plates, there being an annular groove around the innercircumference of each block communi cating with its associated screen plate, a conduit communicating with the uppermost one of said grooves for supplying steam to the reaction chamber, a vapor elf-take conduit adjacent the top of said reaction chamber, a conduit communicating with the lowermost one of said grooves for discharging sugar liquor, and means removing lignin adjacent the bottom of said reaction chamber."

12. Apparatus'asde'fined in claim 11 in which a plurality' of opening's'are provided in each of said annular blocks" whichcommunicate with their associated groove, and in which a plurality of supply conduits communicate wjith'the openingslin theuppermost one of said blocks aplnrality of discharge conduits communicate with the openings in the lowermost'one of said blocks;

13. Apparatus as defined in claim 11 in which each screen plate is provided with a plurality of openings which flare outwardly in the direction of fluid flow therethrough'.

14. Apparatus for treating cellulosic materials comprising a vertically extending reaction chamber having an upper and a lower section, said upper section flaring outwardly toward the bottom thereof and said lower section flaring outwardly toward the top thereof, feed means for introducing a cellulosic material continuously under pressure adjacent the top of the reaction chamber, an outwardly extending annular flange at the lower end of said upper section, an outwardly extending annular flange at the upper end of said lower section, a pair of horizontally extending vertically spaced cylindrical screen plates between said upper section and said lower section, annular blocks surrounding said screen plates, seal means between the lowermost screen plate and block and the uppermost screen plate and block, seal means between said annular flanges and the adjacent screen plates and blocks, means securing the flange at the lower end of the upper section to the flange at the upper end of the lower section, there being an annular groove around the inner circumference of each block communicating with its associated screen plate, inlet conduits communicating with the uppermost one of said grooves for supplying steam to the reaction chamber, outlet conduits communicating with the lowermost one of said grooves for removing sugar liquor, a vapor ofi-take conduit adjacent the top of said reaction chamber, and means removing lignin adjacent the bottom of said reaction chamber.

15. Apparatus for treating cellulosic materials comprising a reaction chamber having outwardly flaring side walls intermediate the ends thereof, feed means at one end of said reaction chamber for introducing continuously thereat the cellulosic materials under pressure, inlet passageways at the opposite end of said reaction chamber for introducing thereat a hot hydrolyzing acid in countercurrent flow to said cellulosic materials, inlet passageways in said reaction chamber intermediate said first mentioned passageways and said feed means for introducing therebetween a hot gaseous medium in countercurrent flow to said cellulosic materials, a vapor oif take conduit communicating with said reaction chamber adjacent said feed means, outlet passageways in said reaction chamber subjacent the second mentioned inlet passageways for removing sugar liquor, and lignin discharge means disposed adjacent said first mentioned passageways for removing substantially continuously tl'xereat the lignin separated in the reaction chamber.

16. Apparatus for treating cellulosic materials as defined in claim 15 in which the longitudinal axis of the reaction chamber is vertically disposed and in which the feed means is adjacent the top of the reaction chamber and the inlet passageways for introducing the hydrolyzing acid are adjacent the bottom thereof.

17. In apparatus for treating cellulosic materials comprising a vertically extending reaction chamber embodying an upper and a lower section, said upper section having downwardly flaring side wall-s and a frusto-conical top therefor, said lower section having a frusto conical bottom, a vertically extending housing mounted adjacent the top of said upper section and having a vertical feed screw mounted for rotation therein for introducing cellulosic material continuously under pressure into said reaction chamber, a horizontally extending housing having a feed screw mounted for rotation therein and communicating with said first mentioned housing for introducing cellulosic material, said second mentioned housing being open at its top, a spray nozzle above said second mentioned housing for spraying acid into the housing, a vapor off-take conduit communicating with said upper section through said frusto-conical top, an inlet conduit communicating with said reaction chamber adjacent the point of juncture of said upper and lower sections for introducing steam, an inlet conduit adjacent the bottom of said lower section for introducing a hydrolyzing acid, an outlet conduit in the reaction chamber subjacent said first mentioned inlet conduit for discharging sugar liquor, and lignin discharge means adjacent the bottom of said frusto-conical bottom.

References Cited in the file of this patent UNITED STATES PATENTS 1,793,084 Griessbach Feb. 17, 1931 2,086,963 Scholler July 13, 1937 2,323,022 Ferrari June 29, 1943 FOREIGN PATENTS 487,014 Great Britain June 14, 1938 545,135 Great Britain May 12, 1942 614,433 Great Britain Dec. 15, 1948 

1. THE METHOD OF PRODUCING FURFURAL AND HEXOSES FROM CELLULOSIC MATERIALS WHICH COMPRISES THE STEPS OF, CONTINUOUSLY BRINGING TOGETHER UNDER SUPERATMOSPHERIC PRESSURE PREACIDIFIED CELLULOSIC MATERIALS IN COUNTERCURRENT FLOW WITH A HOT GASEOUS MEDIUM WHEREBY FURFURAL IS PRODUCED CONTINUOUSLY, REMOVING THE FURFURAL CONTINUOUSLY AS IT IS PRODUCED ADJACENT THE POINT THE CELLULOSIC MATERIALS ARE INTRODUCED, THEN PASSING CONTINUOUSLY THE RESIDUAL CELLULOSIC MATERIALS IN COUNTERCURRENT FLOW WITH A HYDROLYZING ACID AND STEAM WHEREBY SOLUBLE HEXOSES ARE PRODUCED, REMOVING THE SOLUBLE HEXOSES CONTINUOUSLY ADJACENT THE POINT SAID HOT GASEOUS MEDIUM IS INTRODUCED, AND REMOVING THE LIGNIN SUBSTANTIALLY CONTINUOUSLY ADJACENT THE POINT SAID HYDROLYZING ACID AND STEAM ARE INTRODUCED.
 10. APPARATUS FOR TREATING CELLULOSIC MATERIALS COMPRISING A VERTICALLY EXTENDING REACTION CHAMBER HAVING DOWNWARDLY FLARING SIDE WALLS AT THE UPPER PORTION THEREOF, THE UPPER PORTION OF SAID SIDE WALLS FORMING AN UPRIGHT FRUSTOCONICAL TOP AND THE LOWER PORTION OF SAID SIDE WALLS FORMING AN INVERTED FRUSTO-CONICAL BOTTOM, A FRUSTO-CONICAL FILTER SCREEN SECURED TO THE INNER SURFACE OF THE SIDE WALLS AND SPACED FROM SAID UPPER PORTION DEFINING THEREBETWEEN A SECOND CHAMBER, A VAPOR OFF-TAKE CONDUIT COMMUNICATING WITH SAID SECOND CHAMBER, FEED MEANS TO INTRODUCE CELLULOSIC MATERIAL CONTINUOUSLY UNDER PRESSURE ADJACENT THE TOP OF THE REACTION CHAMBER, THERE BEING PASSAGEWAYS IN SAID SIDE WALLS INTERMEDIATE SAID FILTER SCREEN AND SAID FRUSTO-CONICAL BOTTOM FOR INTRODUCING STEAM INTO SAID REACTION CHAMBER, INLET PASSAGEWAYS ADJACENT THE BOTTOM OF SAID REACTION CHAMBER FOR INTRODUCING A HYDROLYZING ACID, THERE BEING OPENINGS IN SAID SIDE WALLS SUBJACENT THE FIRST MENTIONED PASSAGEWAYS FOR REMOVING SUGAR LIQUOR, AND LIGNIN DISCHARGE MEANS ADJACENT THE BOTTOM OF THE REACTION CHAMBER. 